Update links to GitHub docs for access tokens

The action's documentation contains a link to GitHub's documentation about the access token that is provided for use in
GitHub Actions workflows, and another about creating personal access tokens. These pages have been moved since the time
the links were added. Even though the previous page redirects to the new location, it's best not to rely on redirects.

Author: per1234

.github/CONTRIBUTING.md

@@ -28,4 +28,4 @@ See the [official Github documentation][pat-docs] to learn more about Personal A
 1. After the release, rebase the release branch for that major version (e.g., `v1` branch for the v1.x.x tags) on the
    tag. If no branch exists for the release's major version, create one.
 
-[pat-docs]: https://docs.github.com/en/free-pro-team@latest/github/authenticating-to-github/creating-a-personal-access-token
+[pat-docs]: https://docs.github.com/en/authentication/keeping-your-account-and-data-secure/creating-a-personal-access-token

README.md

@@ -105,7 +105,7 @@ Set to `true` to show more information in the log about the checks being run.
 
 GitHub access token used to get information from the GitHub API.
 
-**Default**: [`GITHUB_TOKEN`](https://docs.github.com/en/free-pro-team@latest/actions/reference/authentication-in-a-workflow)
+**Default**: [`GITHUB_TOKEN`](https://docs.github.com/en/actions/security-guides/automatic-token-authentication)
 
 ## Usage